A sealing device typified by a stern tube sealing device of a ship is provided for preventing the inconvenience in function caused due to the entry of a fluid such as sea water into a structure such as a hull and the outflow of the fluid from the inside, and has a single lip seal or multiple lip seals including an elastic body such as rubber or elastomer provided for a shaft hole through which a shaft is inserted.
A lip seal is slidably in hermetic contact with (hereinafter referred to as seals) a surface of a shaft and maintains the straining force on the shaft with the elastic force of the lip seal itself, the pressure applied by a spring or the like, a fluid pressure difference on front and back faces of the lip seal, or the like. As for the operation of the elastic force of the lip seal itself and the like, first, sealing is performed through elastic deformation of a lip part (for example, see Patent Document 1 below), second, sealing is performed while the value of an interference is adjusted by air spring type sealing (see, for example, Patent Document 2 below), and third, sealing is performed by a straining force applying means attached to the seal lip for applying a straining force to the lip seal for pressing the lip seal against a shaft (see, for example, Patent Document 3 or Patent Document 4 below).